A boundary integral method is adopted to simulate thebubble motion in the fluid field on the assumption that the fluid field isinviscid, irrotational and incompressible. A corresponding three-dimensionalcomputation program is exploited and the calculated results agree well withthe experimental data. The interaction between multiple bubbles near thefree surface including in-phase and out-of-phase bubbles is simulated withthe program presented here. From calculation it's found out that the bubbleperiod increases along with the decrease in the distance between bubblecenters because of the depression effect among multiple bubbles and theeffect is more evident especially for out-of-phase bubbles. The depressioneffect exists between all bubbles no matter whether there is a free surfaceor not. There are great differences on the dynamic behavior of in-phasebubble coupling and that of out-of-phase bubble coupling due to thedepression effect. These phenomena can provide reference for the futureresearch on the power of underwater explosion bubble induced by multiplecharges exploding simultaneously or continuously.